Do Aliens Exist in the Milky Way?

Our home galaxy, the Milky Way, is a pretty big place. It harbors 200 to 400 billion stars and spans roughly 100,000 light-years from one edge to the other. (To put it in perspective, Earth is only about 8.3 light-minutes from our own star, the sun.) This is one reason why some scientists feel that alien civilizations are common in the galaxy, possibly numbering in the tens of thousands, and why a small band of astronomers have devoted themselves to the Search for Extraterrestrial Intelligence (SETI). Yet other scientists think we humans are the only creatures in this vast neighborhood with the smarts and technology to communicate across space.

What do you think? Are there aliens in the Milky Way capable of communicating with us?

You'll answer this question repeatedly through the course of our poll, as you explore a series of arguments pro and con. At first, you can answer Yes or No, and each time, depending on how you vote, we'll show you an argument meant to challenge your stance. (We're playing devil's advocate on both sides!) After your final vote, which you can cast as Yes, No, or Undecided, you'll see how others have responded. To launch this interactive, click on the image at left.—Susan K. Lewis